The present invention pertains to improvements in the design of particulate filter assemblies using a filter means and filter holding means that are used for real time particulate mass collection systems such as those described in the following patents: U.S. Pat. Nos. 7,285,736 and 6,444,927 and 6,205,842 and the many other variants utilizing a filter collection means integrated with a filter holding means to comprise a filter assembly for the purpose of collecting particulate in real time.
In these patents, a filter and filter holder is affixed to the end of a resonant structure, much like a tuning fork, and the mass of the filter is proportional to the frequency of oscillation. In these examples, the filter and filter holder are one and the same and the filter is not replaceable. In other words, the filter holding means are integrated into a single filter assembly where the filter collection means is securely fastened, to prevent leaks, to the filter holding means.
In practice, a clean filter and filter holder are attached to the end of the resonant structure and the resonant frequency of the filter and filter holder is recorded. As the filter loads up with particulate the mass of the filter and filter holder increases. Using the differences of resonant frequencies, one can infer the mass of the filter and filter holder in real time.
Problematic with existing filter and filter holder design is that they are relatively heavy. In know devices, weigh reduction has been pursued by reducing the mass of the filter holding means utilizing various geometrical designs that still maintain sufficient strength and rigidity to allow the filter holding means to survive in the operational environment. The present invention departs from this approach in accomplishing a goal of weight reduction to improve device performance. The present invention optimally offers other improvements to device performance as well.